Flame failure control for a vapor oenerator burner system



July 20, 1965 J. A. scHuss ETAL 3,195,610

FLAME FAILURE CONTROL FOR A VAPOR GENERATOR BURNER SYSTEM Filed Nov. 29,1962 s Sheets-Sheet 1 FIG.3

INVENTORS: JACK A. SCHUSS VIRGINIUS Z. CARACRISTI BYyMJW ATTORNEY July20, 1965 J. A. SCHUSS ETAL 3,

FLAME FAILURE CONTROL FOR A VAPOR GENERATOR BURNER SYSTEM Filed Nov. 29.1962 s Sheets-Sheet 2 ,//0 kas PIC-3.5

INVENTORs: JACK A. SCHUSS VIRGINIUS Z. CARACRISTI MWJM ATTORNEY J y 1965J. A. scHuss ETAL 3,195,610

FLAME FAILURE CONTROL FOR A VAPOR GENERATOR BURNER SYSTEM Filed Nov. 29,1962 3 Sheets-Sheet 3 SQJ kmilquw INS-3k INVENTOR. JACK A. SCHUSSVIRGINIUS Z. CARACRISTI ATTORNEY Unitcd States Patent FLAME FAILURECQNTRQL FER A JAFGR GENERATOR BURNER SYSTEM Each A. Schuss, Hartford,and Virginius Z. Caracristi,

West Hartford, Conn., assignors to Combustion Engineering, Inc Windsor,Coma, a corporation of Belaware Filed Nov. 25 1962, him. No. 24%,797

it) Ctaims. ((1 158-28) The present invention relates to a novel burnercontrol system for a vapor generator. More particularly, the inventionrelates to a system for controlling the admission of fuel to the burnersof a vapor generator only at such times that suflicient ignition energyexists as will ignite the fuei.

In the operation of a vapor generator there exists the danger ofadmitting fuel to the burners and thence into the furnace chamber whenthere is no flame with which to provide suflicient ignition energytoignite and burn the fuel thereby resulting in the creation of afurnace atmosphere which is highly explosive. To insure the safeoperation of a vapor generator, it is necessary to provide some meansfor preventing the establishment or" an explosive atmosphere within thefurnace chamber.

With the advent of larger vapor generators capable of creating greateramounts of vapor and the tendency of operating vapor generators on acompletely automated basis, the problem of safe operation is increased.In the first place, larger vapor generators require a greater number ofbur ers for producing heat of combustion and a concomitant greatervolume of fuel to be burnt. The increase in the number of burners andthe volume of fuel admitted to the furnace thus enhances the explosivepotential of the generator thereby requiring means to constantly monitorthe burner system to insure that a flame exists to burn all of the fueladmitted to the burners and to take the appropriate steps to discontinuethe admission of fuel to the burners when the flame at the burners orwithin the furnace chamber for some reason ecomes extinguished. On theother hand, the introduction of completely automatic means to overseethe operation of a vapor generator makes it necessary to insure thatthese means function properly such that an explosive condition cannotexist within the furnace. The utilization of automatic control meansremoves the operation of the vapor generator from the hands of anoperator and relies solely on the proper functioning of the variouscomponents employed in the control system organization. This fact couldhave a tendency to reduce the economy of operation of the generator bymaking possible the occurrence of so-called nuisance shutdowns, or thoseshutdowns instigated by a malfunction of one of the control systemcomponents rather than by the condition of the furnace.

The herein disclosed invention contemplates providing a completelyautomated control system which will con tinuously monitor the burnersand will discontinue the admission of fuel thereto immediately upon itsbecoming evident that there is insufficient flame with which to burn thefuel admitted to the furnace chamber and thereby prevent the creation ofan explosive atmosphere therein. The system is so organized as torequire the concurrence of two independently operable flame monitoringmeans which monitor different aspects of burner firing before the vaporgenerator can be shut down thereby tending to eliminate the occurrenceof nuisance shutdowns.

The control system is operative during three principal phases of burneroperation to maintain the furnace chamher in a non-explosive condition.During the first phase, i.e. startup of the burners, means are operativeto prevent the admission of fuel to each of the burners on an individualbasis until the igniters associated with each of ildifild Patented July20, 1965 ice the burners exhibit sufiicient ignition energy with whichto insure ignition to the burners thereby obviating the danger ofadmitting fuel to burners whose igniters are in operation but whichoperation is not sufiicient to ignite the burners. The means employedcomprises pressure differentiating means associated with the igniterswhich are capable of determining the magnitude of ignition energyavailable at the igniter and, when a sufficient amount of ignitionenergy is present, actuating the fuel supply valve associated with theburner to its open position. This phase of Control continues until thesupply valve reaches its full open position at which time the secondphase of burner control is initiated. This second phase involves thedetermination of whether or not the fuel supply valve should bepermitted to remain open. The means provided for such determinationinclude the same igniter pressure differential sensing device whichoperates in conjunction with an optical flame sensor arranged to viewthe existence or nonexistence of flame at the mouth of the burner. Theoptical flame scanner is operable independently of the igniter pressuredifferential sensing means and serves to back up or augment theoperation of the former thereby permitting its removal from service formaintenance purposes without having to shut down the burner. The thirdphase of control is initiated when the flame developed within thefurnace chamber by the operation of the burner system is sufficientlylarge to reignite any of the burners which would happen to lose theirsource of independent ignition energy. During this phase of operationall of the igniter pressure differential sensing means and the opticalflame scanners are so organized as to integrate the monitoring of eachof the burners on an overall furnace chamber basis. During this phasethe control system is arranged to dis continue the admission of fuel toall of the burners simultaneously, such discontinuation occurring onlywhen both groups of flame sensing means register the nonexistence offlame at a sufiicient number of burners to demand shutdown of thegenerator.

In the herein illustrated vapor generator the burner system comprisesthree burner elevations each consisting of four burners. The point ofhazardous operation of such a vapor generator is considered to be thatpoint where there is a total absence of flame within the furnace chamberor where all of the burners of each elevation show no flame. However,the present control system presupposes the possibility of a portion ofthe monitoring system failing on the unsafe side, i.e. registering thepresence of flame when, in fact, none exists and so instates a factor ofsafety in the control of the burner system by considering each burnerelevation to be inoperative when any three of the four burners whichcomprise the elevation show no flame.

The invention is predicated upon the existence of two completelyindependent flame monitoring systems, one of which monitors the ignitersemployed to provide ignition energy for the fuel which issues from eachburner and the other of which is a line of sight device which overseesthe flame condition existing at the mouth of the burner itself. Whilethe former is associated with the igniters and not with the burnersthemselves, it remains a valid means for determining the flame conditionexisting at the burners since it is a pressure differential sensingdevice which is capable of determining whether sufficient ignitionenergy exists at the igniter to ignite the burners when fuel is admittedthereto. Therefore, by deduction, if fuel is admitted to the burners andthe igniters exhibit sufficient ignition energy to ignite the fuel,there must be a flame existing at the burner.

Because of the special interrelationship between the two flamemonitoring systems during the third phase of burner operation, a vaporgenerator, once put in operation, cannot have its operation discontinueduntil such time as the furnace conditions demand a cessation ofoperation as proven by a concurrence of the two monitoring systems. Thisfeature lends itself to the development of a more dependable generatorcontrol system since the possibility of experiencing a shutdowninstigated by failure of one of the components of the control systemrather than by the nonexistence of a flame within the furnace isvirtually eliminated. Each of the monitoring systems, in effect,oversees the operation of the other and effects a shutdown of thegenerator only when both of the systems experience the nonexistence offlame thereby reducing the possibility of having nuisance shutdownswhich, in turn, results in a reduction of the expense and annoyance ofhaving to remove a generator from service merely because of amalfunction in the control system.

In addition to reducing the expense and annoyance caused by nuisanceshutdowns, there is also eliminated one of the hazards of generatoroperation during the occurrence of which it has been shown thatexplosions are most apt to occur. This condition is that which existsduring the startup of a vapor generator Where, due to the instability ofthe furnace atmosphere, the explosive potential of the generator is atits highest. By reducing the number of times the vapor generator iscompelled to shut down the number of times it must pass through thestartup'cycle is also reduced thereby enhancing the safe operation ofthe unit.

It is therefore an object of the present invention to provide a controlsystem for an automated vapor generator which is capable of dependablymonitoring the flame condition existing within a furnace chamber andinitiating measures to prevent the creation of an explosive atmospheretherewithin.

Another object of the invention is to provide a control system for anautomated vapor generator which will not occasion a shutdown of thegenerator because of a malfunction in a portion of the system itself butwill insti-' gate measures to discontinue the admission of fuel to thefurnace only when the furnace conditions themselves require suchdiscontinuation.

An additional object of the invention is to provide a control system foran automated vapor generator which will discontinue the admission offuel to the furnace even though a portion of the flame monitoring systemmalfunctions in a manner which would tend to maintain continued fueladmission.

A still further object of the invention is to provide an automaticcontrol system for a vapor generator which is structurally simple yetoperably dependable.

Other and further'objects of the invention will become apparent to thoseskilled in the art as the description proceeds.

. With the aforementioned objects in view, the invention comprises anarrangement, construction and combination of the elements of theinventive organization in such a manner as to attain the results desiredas hereinafter more particularly set forth in the following detaileddescription of an illustrative embodiment, said embodiment being shownby the accompanying drawings wherein:

FIG. 1 is a diagrammatic illustration of, a vapor generator of the typeintended to employ the instant invention;

FIG. 2 is a diagrammatic cross-sectional plan view of the furnacechamber of the generator shown in FIG. 1;

FIG. 3 is a schematic representation of a fuel supply valve employed inthe present invention;

FIG. 4 is an enlarged plan view of one of the corners of the furnaceshown in FIG. 2 in which is illustrated a typical burner installationincorporating an igniter, igniter sensor and flame scanner organizationas contemplated by the present invention;

FIG. 5 is a wiring diagram of the control system utilized in effectingthe individual burner protection concept in accordance with the presentinvention; and

PEG. 6 is the wiring diagram employed in organizing the components ofthe control system utilized in monitoring the overall operation of thegenerator in accordance with the present invention.

Referring now to the drawings there is shown in FIG. 1 a vapor generatorMP comprising a furnace chamber 12 having outer walls lined with uprightvapor generating and Wall cooling tubes 14 which are interconnected influid circulation whereby a vaporizable liquid, most commonly water, istransformed into vapor by the addition of heat extracted from combustiongases generated in the furnace chamber. Burners 16 are positioned atspaced points about the furnace chamber 12 and are supplied with fuel bymeans of fuel supply lines 18 which connect the burners with a supplysource (not shown) through a main header 2% and main fuel line 22. Themain header contains a pressure switch 24) which is actuated upon ex-' 7periencing a fuel pressure within the system which representssubstantially 30 percent of rated fuel pressure for the burners. lnthemain fuel line 22 between the main header Zll and the supply sourceis located a main supply valve 24 having an electrically actuated valveoperator 26 which controls the admission of fuel to the main header 2t}and thence to the supply lines 18. Fuel supply valves 23 are provided inthe lines 18 to control the admission of fuel to each burner 16. Thesevalves 28 have operators 3ft which effect a slow opening but rapidclosing of the lines 18;

A typical valve of this type is shown in FIG. 3. Its actuator 3-9comprises a hydraulically actuated piston 32 which is operable within acylinder 33 and which operates a valve stem 34 against the force of aspring 35 by means of fiuid pressure. Fluid is supplied to the underaside of the piston 32 through inlet line 39 by means of a pump 4% whichis driven by an electric motor 42. A normally closed limit switch 44 isinterposed in the motors power line and operates to discontinueoperation of the motor once the valve stem 34 has reached its upper mostposition thereby indicating that the valve 28 is open. The switch 44- isopened by means of an arm 46 which is attached to the valve stem 34. Apressure relief valve 4% operated by a solenoid l9 is associated withthe pump 4i? such that fluid pressure admitted to the cylinder 33remains to maintain the valve 23 in its open position after operation ofthe pump motor l2 has been discontinued until such time as the solenoid49 is actuated to open the relief valve 33 thereby venting the fluidbeneath the piston 32 and permitting the valve stem 34 to descend underthe force of spring 36 to rapidly close the valve 28.

The vapor generator ill comprises a plurality of burner elevations,designated as I, II and III, which may be operated singly or in unisondepending on the load requirements of the generator. Each elevationconsists of 7 four burners 16, each of which is located in one of thefour corners of the furnace 12 for discharging streams of fuel and airfor burning in directions tangential to an imaginary firing circle 5thas shown in FIG. 2. For the sake of clarity the'burner assemblies ateach of the corners of the furnace 12 have been designated as A, B, C

v and D.

FIG. 4 illustrates a typical burner assembly at one of the corners inthe furnace 12. mounted in the corner of the furnace 12 having meansassociated therewith to permit the admission of fuel and Closelyadjacent to the burner 16 is air for burning. riibunted an igniter torchassembly 52 which comprises a mounting plate 54, torch head 56, nozzel58, and spark plug 60. The mouting plate 54 supporting the igniter torch52 is attached to the furnace casing 63. Fuel is V admitted to'thenozzel 58 through an inlet line 66 which contains a diffusing element oratomizer for'eifecting the diifusion of fuel prior to its emergence fromthe nozzle 58 and ignition by the spark plug so. The igniter torch 52 isoriented with respect to the burner 16 such that the It comprises aburner N flame produced by the ignition of fuel admitted thereto isdirected into the path of the combustion elements issuing from theburner in so as to effect their ignition.

The operation of the vapor generator thus far described is as follows:Fuel, which may take the form of oil, gas or the like, is admittedthrough the main fuel line 22 when the main supply valve .24 is in anopen position. Header ill effects distribution of the fuel to each ofthe fuel supply lines which have interposed there in independentlyoperable supply valves 28 controlling the admission of fuel to each ofthe burners 16. The fuel admitted to the burners is ignited by the pilottorches 52 thereby producing a flame and gasses of combustion within thefurnace chamber 12. At the same time, vaporizable fluid in the form ofwater is admitted to the tubes f4 and caused to flow therethroughextracting heat from the combustion gases to thereby effect atransformation of the fluid into vapor. The amount of vapor generatedwithin the tubes 14 depends on the number of burner elevations which areput into operation with the generators total capacity being developedwhen all of the elevations I, H and III are operable and lesser amountsbeing generated with a lesser number of elevations operating.

The present invention contemplates providing means to prevent thepossibility of permitting unburnt fuel to accumulate within the furnacechamber 12 where it would subject the unit to the possibility ofexplosion. This means includes control of the admission of fuel to eachof the individual burners of a multi-burner system during one portion ofthe operative cycle of the vapor generator and control of the admissionof fuel to all of the burners of said system in response to the overallcondition of the furnace during the remaining portion of the operativecycle. By means of the present organization the entire operation of thegenerator is subject to control by the system thereby enhancing theoverall safety of the generator operation.

The control system organization is predicated upon certain factors.First, once the fuel loading of the burners reaches a certain point andignition thereof has been achieved, there will exist within the furnacechamber a fireball of sufiicient volume to ignite the fuel issuing fromany burner even though its individual source of ignition has beenremoved. This point is taken to be 30 percent of burner capacity.Second, the fireball can be maintained at a sufficient volume as long asat least two of the burners of a given elevation in the hereindisclosedburner system are firing. Therefore, fuel issuing from all of theburners of every elevation can be ignited by the fireball created by twoof the four burners of any single elevation.

The control system includes a monitoring system for determining theflame conditions of the furnace and burner system and means activatedthereby to discontinued the admission of fuel to the burners when theflame conditions so require. The monitoring system employed to overseethe operation of the vapor generator comprises a pair of completelyindependent monitors associated with each of the burners capable ofmonitoring the condition of the burner and creating an electrical signaladapted to produce the desired control function. One of the monitors isa pressure differential measuring device, generally indicated as '70which is adapted to register the pressure differential existing withinthe igniter head 56 to determine the amount of ignition energy availabletherein with which to ignite the adjacent burner lb. The measuringdevice contemplated in the preferred embodiment of the invention is asdescribed in US. Application Serial No. 205,483 to Livingston, filedJune 19, 1962, now Patent No. 3,123,027, granted March 3, 1964. Itcomprises a pair of pressure taps '72 and 74 which communicate with theigniter head 56 at spaced points therealong. One tap '72 communicateswith the head se at a point adjacent the nozzle 58 and the other tap '74communicates with the head at a point adjacent the mouth thereof. Thetwo pressure taps 72 and '74 communicate with a pressure differentiatingchamber 75 on either side of a diaphragm 78 retained therein. To thediaphragm 73 is attached an arm 3% adapted to close contacts 32 whicheffect actuation of a multiplying relay 84. The relay 84 serves to closecontacts 36 indicating that there is suficient ignition energy withwhich to ignite the burner 15 or that the igniter is on and contacts 58,9t and 9b which are closed by the relay 84 being in its deactuatedposition indicating the absence of suflicient ignition energy in theigniter S2 or that the igniter is off. Contacts 86 and 38 are thosecontained in the control circuit shown in FIG. 5 pertaining to theindividual burner control system and contacts 9% and 90' are thosecontained in the control circuit shown in FIG. 6 pertaining to theoverall generator control system.

The other monitoring device generally indicated as 5 2 is an opticalflame scanner arranged within the burner to such that its line of sightis oriented so as to enable it to register the existence or nonexistenceof flame at the mouth of the burner through circuitry as described inUS. application Serial No. 235,098 to Gilbert, filed November 2, 1962,of the s me assignee. The flame scanner 2 comprises a photo-sensitiveelectron tube 94 mounted adjacent to the mouth of the burner 16 and areceiver as which is capable of transforming the electric signalreceived from the electron tube 94 into means effective to closecontacts $8 which, in turn, effect actuation of a multiplying relayIlfiti. The relay 1% is so arranged as to close contact 16 2 in itsactuated position indicating the presence of flame at the mouth of theburner in or that the burner is on and to close contacts 1%, ice and icein its deactuated position indicating the absence of flame or that theburner is off? Contacts 62 and we are those contained in the circuitryemployed in the individual burner control system of MG. 5 and contactsfile and we are those contained in the circuitry employed in the overallburner control circuit of FIG. 6.

The control circuits illustrated in FIGS. 5 and 6 are those employed tocontrol the admission of fuel to the burner 15 during the threesignificant phases of vapor generator operation, the first phase beingthe initial startup of the burners 16 during which time it is imperativethat the igniters 52 exhibit sufficient ignition energy to light off thefuel admitted to the burners This phase of generator operation isgoverned by the individual burner control system, the circuitry of whichis shown in F16. 5. The purpose of this system is to insure that no fuelwill be admitted to the burners 16 until such time as the respectiveigniters 52 associated with each of the burners is providing sufficientignition energy with which to ignite such fuel as determined by theigniter sensor 70. When the sensor 7d determines that there issufficient ignition energy at the igniter 52, the fuel supply valve 23associated with the burner 16 is permitted to open thereby admittingfuel to the burner. When the valve 28 becomes fully open, thearrangement of this portion of the control system permits the valve toremain open provided any one of the following conditions exist: that theigniter sensor '79 continues to show sufiicient ignition energy in theigniter 52, that the optical flame scanner $2 witnesses the existence offlame at the burner 16 or that the pressure switch 2% in the main fuelheader 2% is closed indicating that the load on the burner is at leastas great as 30 percent of the rated burner load.

With reference now to FIG. 5 the circuitry involved consists of powersupply leads 1H? and 112 and a line 114 containing the motor 42 for thefuel supply valve actuator 30 for the valve 28. All of the valves 2% inthe system contain a similar circuit so that, in order to avoidrepetition, only one circuit will be described here. The line 114contains contacts 136 which may be manually closed by means of a doublepole, double throw switch 118 or the circuit may be completed by anequivalent conv 2? tact closure by m ans of a signal received from acomputer (notshown). Connected in series with the contacts 116 arecontacts 1% and 44, contacts 86 being those which are closed when theignit-er sensor 7%) indicates the presence of theproper amount ofignition energy in the igniter to ignite the burner 16 and contacts 44being those associated with the fuel supply valve 28 shown in FIG. 3indicating that the valve is fully open. Contacts 45 which are alsoassociated with the valve stem 34 to be closed when the valve is fullyopen are par-allelly related with'the contacts 86. in series with'thecontacts 45 are'parallelly connected contacts 21 and 1&2, contacts 162being those associated with the optical flame scanner 92 indicating whenclosed that the electron tube 94 witnesses the presence of flame at themouth of the burner 16 and the contacts 21 being those which are closedwhen the pressure switch in the main header Zti senses a fuel pressuretherein which is at least as great as 30 percent of that pressureassociated with rated burnor load. By means of this arrangement, thevalve actuator motor 42 is operable initially after the control switch118 closes contacts 116 only when the igniter sensor "79 determines thatthere is sufficient ignition energy to ignite the burner 16 andthereafter, once the fuel supply valve 28 reaches its full open positionand contacts 45 are closed the valve can remain open if either theigniter remains on or the optical flame scanner 92 manifests thepresence of flame at the mouth of the burner 16 or the fireball withinthe furnace chamber 12 is of a sufiicient size to reignite the fuelissuing Tom the burners 16 should their source of independent ignitionbe removed.

In order to close the valve 28, it being of the energize toopen-energize to close type, the solenoid 4% must be actuated to openthe relief valve 4% in the actuator 3t of the fuel supply valves 23. Toaccomplish this the alternate circuit shown as line 12% containingsolenoid 4% is provided in parallel with line 114. It also containscontacts associated with the same apparatus as are rep-resented in line114 but which are closed upon the existence of conditions whichrepresent the opposite of those covered by the contacts in line H4. Asshown, line 12*!) contains contacts 122 which are associated with thecontrol switch 1-18 and closed when it is desired to close the valve 23manually or upon a signal received from a computer.

In parallel with the contacts 122 are contacts 88, connected in serieswith the parallel arrangement containing contacts 4?, m4 and 21'.Contacts 83 are those which are closed when the i-gniter sensor 7@indicates that the ignition energy available at the igniter isinsufficient to ignite the associated burner. Contacts 47 are thoseassociated with the valve 28 which is normally closed until the valvereaches its fully open position and contacts 184- are those associatedwith the optical flame scanner 92 and closed when the scannerexperiences a condition of noaflame at the burner. those that are closedwhen the pressure switch in the main header 2% experiences a fuelpressure representative of less than 30 percent of rated burnercapacity.

A circuit diagram for the overall generator control system isillustrated in FIG. 6. Like contacts have been designated by likenumerals but are sufiixed by an appropriate designation of the corner ofthe furnace in which the associated burner is located. Lines 124 and 126are the power supply leads across which are connected in parallel theigniter sensor circuit and the optical flame scanner circuit designatedgenerally as 128 and 13%} re-- spectively and line 14% ,in which islocated a bank of parallelly connected contacts 45 associated with thefuel supply valves 28 in such a manner as to be closed when the valveachieves a full open position. Connected in series with this bank ofcontacts 45 are contacts 136 and 138 associated with the igniter sensorcircuit'l23 and the optical scanner circuit 136 which are closed uponactuation of relays 132 and 134 as governed by the monitoring circuits128 and 130. Also connected in series in line Contacts 21 are 14th is arelay 142'the actuation of which serves to close contacts 144 operatingthe main fuel supply valve actuator 26 to close the valve 24.

The igniter sensor circuit 128 comprises a series-parallel circuitarrangement in which are contained the contacts 9t? and 9% associatedwith the igniter sensor relay 84 which is actuated when the ignitersensor ill registers the absence of sufficient ignition energy withwhich to ignite the adjacent burner 16. The circuit 128 extends from thelead'lZd to the lead 112s terminating at the latter in re lay 132; whichis actuated upon completion of the circuit. This circuit 128 comprises aseries-parallel arrangement'of the contacts W and 9h", the closure ofwhich is governer by the relays 84 operated by the igniter sensors 79associated with the four corners A, B, C and D of each elevation I, IIand III. The series-parallel arrangement shown permits a closure of thecircuit across the respective elevational portions thereof as long asthe igniter sensors '78 associated with any three of the four burnerswhich are located in the elevation exhibit an insufficient amount ofignition energy. Included in this circuit are lines ldfi which createavenues of passage for the electric current'through each of theelevational portions of the circuit to the relays 132. Connected acrosseach of the elevational portions in parallel with the series-parallelarrangement of contacts @0 and 9% are contacts 148 which are associatedwith the control switches which can either be manually operated orreceive its actuation from a computer signal the closure of which iseifected'when it is desired to remove a particular burner elevation fromservice or to remove the igniters of an elevation for maintenancepurposes to short circuit that elevational portion of the circuit 123which is equivalvent to the igniter sensors registering an insufficientamount of ignition energy in that elevation.

The short circuiting of'that elevational portion of the igniter sensorcircuit 128 which is removed from service is necessary because theigniter flames for anyone burner elevation are not suihcient to ignitefuel which issues from the burners of another elevation. Therefore, thatportion of the control circuit associated with such igniters mustindicate that the igniters'are incapable of igniting any fuel admittedto other burners.

The optical flame scanner circuit is similar to the igniter sensorcircuit 128 in that the same series-parallel arrangement of contacts 106and lfiflexists. As in the circuit 123, this arrangement of the contacts1% and 1% which are actuated by the relays 1% associated with each ofthe optical flame scanners 92 efiects a closure of the circuit in thatelevational portion of the generator when'the optical flame scannersassociated with any three of the four burners located in that elevationexperience the absence of flame in the burner 16.

The operation-of the complete control system is as follows: duringstartup of the generator each of the burners 16 is governed by theirrespective individual burner control circuits such as that shown in FIG.5. When it is desired to place a burner in operation, the control switch118 must first be actuated to close contacts 116. If the ignitcr sensor79 associated with that burner exhibits the presence of suflicientignition energy in the igniter 52 with which to ignite the burner oncefuel is admitted thereto, contact 36 will be closed thereby permittingthe flow of current to the valve actuator motor 42 and contact 8$ willbe open thereby deactuating the solenoid 49 closing the internal reliefvalve 48 thus permitting the valve 28 to open. Once the valve 28 isopen, the second phase of control function comes into play with theclosure of contacts 45and opening of the contacts 47 associated with thevarious fuel supply valves 28. During this phase the fuel supply valves28 will remain open as long as either there is sufficient ignitionenergy being provided by the igniter 52 thereby keeping contacts 86closed and with the burner 15 experiences the presence of flame at theburner thereby effecting the closure of contacts W2 and the opening ofcontacts 104 or the pressure within the main header it) indicates thatthe burner load is at least 30 percent of rated burner capacity in whichcase the ball of fire or flame envelope within the furnace chamber is ofa sufiicient size to maintain ignition of the fuel being admitted to theburners thereby efiecting closure of contacts 21 and opening of contacts21'. If, on the other hand, none of these conditions exist, the circuitcontained in alternate line 12 will be closed and the circuit in line114 will be open thereby etfecting immediate closure of the valve 28.With the opening of any valve 28, contacts 45 associated with that valveare closed thereby putting into operation the overall generator controlcircuit shown in FIG. 6.

When the contacts 45 are closed putting the overall generator controlcircuit initially into operation, the individual burner control circuitsshown in PEG. 5 continue to primarily govern the operation of the fuelsupply valves 2% until and unless the contact 21 associated with thepressure switch 19 is closed with the overall generator control circuitserving as a backup system to close the main fuel valve 24 todiscontinue operation of the entire generator only in case of a totalflameout. Upon closure of contacts 21, however, the generator undertakesthe third phase of its operation this being the phase in which thefireball within the furnace chamber 12 is of a large enough volume toinsure reignition of the fuel admitted to the burners 16 should theylose their independent sources of ignition. At this time control of thefuel admission to the generator through the valve Ed is undertakenexclusively by the overall generator control circuit. Control of thegenerator in accordance with this concept is embodied in the circuitryshown in FIG. 6 and relies on the monitoring of each burner in thegenerator by both the igniter sensor '70 and the optical flame scanner92. To discontinue operation of the vapor generator during this phasethe control system must indicate that all of the burners in eachelevation have been extinguished. However, in order to prevent thefailure of control system operation due to some component failure on theunsafe, side, i.e. where the monitors indicate the presence of flamewhen none in fact exists, the control system is so organized that therewill be an indication of total flameout in each elevation when themonitors associated with any three of the four burners located in eachelevation indicate an absence of flame. There is thus provided a 25percent margin of safety against component failure on the unsafe side.Moreover, there must be a flameout manifest in all of the burnerelevations before the control system is operative to close the main fuelsupply valve 24. The series-parallel arrangement of contacts 99 and 90"for each of the burner elevations is circuit 128 permits the closure ofthe circuit when the igniters associated with three of the four burnersexperience an absence of flame. For example, assuming corners A, B and Cin elevation I, corners A, C, and D in elevation 11 and corners B, C andD in elevation III have ceased to fire. Should this happen, contacts90A, 9813, %C, %'A, 993 and 98C in elevation I would be closed therebyeffecting closure of the circuit through contacts il'B, 96'A, and )Il'C;in elevation If contacts 99A, 90C, 98D, 9tlA, 9%C and 9WD would beclosed thereby establishing closure of the circuit through contacts 90A,95C and S'iiD; and in elevation HI contacts 941B, 99C, 90D, 9W3, 9313and QiiC would be closed thereby establishing closure of the circuitthrough contacts 9813, 90D and 9llC. There is thus established a closureof the circuit through contacts 9W3, 90'A and 990 in elevation I, 90A,sac and 981) in elevation II and QQ'B, 9WD and fitl'C in elevation IIIto effect actuation of the relay 132 thereby closing contacts 135 inline 14%.

Similarly with regard to the optical flame scanner circuit 130, inelevation 1 contacts ltitSA, 166B, 106C, ltldA, 1688 and lilC will beclosed establishing a complete circuit across elevation 1 throughcontacts ltloB, liidA and ldd'C; in elevation 711 contacts 166A, 106C,1WD, :lltid'A, 1%0 and lltitil) would be closed establishing a completedcircuit across elevation 11 through contacts ltlfiA, 1436C and M561); inelevation Ill contacts 1MB, 195C, D, was, lilt'r'C and iit-fiD will beclosed establishing completion of the circuit across elevation 111through contacts lltieB, D and 1636C thereby effecting actuation ofrelay 134 and closure of contacts 133 in line 1449. With the closure ofcontacts 136 and 138 in line 14-h there is established a completedcircuit through that line thus permitting the passage of current fromthe live lead 124 to actuate the relay 1&2 thereby closing contacts 144to effect actuation of the main fuel valve operator 26 which effectsclosure of the main fuel supply valve 2d. Closure of the main fuelsupply valve 24 effects a discontinuation of the admission of fuel toall of the burners 16 in the generator thereby effecting a totalshutdown of the unit.

When it is desired to operate the generator under conditions of partialload with only one or two of the burner elevations in operation, thatportion of the igniter sensor circuit 12% associated with the elevationwhich has been removed from service will be short-circuited by closureof contacts 1 58 even though the associated igniters are on. Thisclosure will be effected by means of a manual control switch as shown inFIG. 6 or by means of a signal received from the computer.Short-circuiting that portion of the circuit 128 simulates theregistration of a no-fire condition by the igniter flame sensors 7t!)related to the burners in that elevation. The remaining portions of thecircuit are operable as was described above so that a cessation of flamein any of the operating burner elevations will efiect actuation of therelay 132. The optical flame scanner circuit 13d requires no comparableshortcircuiting provisions due to the fact that it involves line ofsight devices which will naturally register no-flame with viewing theburners of an elevation that is not in service.

From the foregoing description it can be seen that the present burnercontrol system provides a highly efi'icient means for safeguarding theoperation of a vapor generator against explosion. The system is operablethrough each phase of the generator operation cycle to prevent thecreation of an explosive atmosphere within the furnace chamber.Moreover, the present organization furnishes a means for automaticallyinitiating the admission of fuel to the burners only when the ignitersare capable of igniting it and also discontinuing the admission of fuelto the burners when it becomes evident that there is insufficientignition energy by which it can be ignited.

The arrangement of components is such that removal of a generator fromservice will occur only when furnace conditions so require not becauseof component malfunction. Means are additionally provided to effectshutdown of the generator even though component malfunction may be suchas would tend to continue the admission of fuel to the burners in spiteof the fact that there is no ignition energy with which to ignite it.

There is thus provided a simple, yet highly flexible control system foruse in a multiburner vapor generator capable of automatically preventingthe creation of an explosive atmosphere within a furnace chamber over abroad range of generator operation.

While particular embodiments have been described and illustrated,various modifications may obviously be made without departing from thetrue spirit and scope of the invention which is defined by the appendedclaims.

What is claimed is:

l. The combination of a furnace chamber; a burner adapted to fire insaid furnace chamber; a fuel line connecting said burner to a fuelsource; a valve interposed in said fuel line; a signal responsive valveoperator adapted to open and to close said valve; an igniter forigniting said burner; first sensing means adapted to emit a signal whenthe ignition energy output of said igniter is sufficient to ignite thefuel admitted to said burner; second sensing means associated with saidburner adapted to emit a signal when said burner exhibits a flame; thirdsensing means associated with said valve adapted to emit a signal whensaid valve is substantially fully open; means connecting said sensingmeans and said operator for opening said valve upon receipt by saidoperator of a signal from said first sensing means and means for holdingsaid valve open upon receipt of a signal from said second and thirdsensing means.

2. The combination of a furnace chamber; a burner adapted to lire insaid furnace chamber; a fuel line connecting said burner to a fuelsource; a valve interposed in said fuel line; operator means adapted toopen and to close said valve; an igniter for igniting said burner; firstsensing means including a normally open switch adapted to close when theignition energy output of said igniter is suificient to ignite the fueladmitted to said burner;

second sensing means including a normally open switch adapted to closewhen said burner exhibits a flame; third sensing means including anormally open switch adapted to close when said valve is fully open;circuit means containing said switches for actuating said operatorincluding a line for opening said valve upon closure of the switchassociated with said first sensing means and a line for holding saidvalve open upon the simultaneous closure of the switches associated withsaid second and third sensing means.

3. The combination of a furnace chamber; a burner adapted to fire insaid furnace chamber; a fuel line connecting said burner to a fuelsource; a valve interposed in said fuel line; operator means adapted toopen and to close said valve; an igniter for igniting said burner;

first sensing means comprising a pressure differential sensor associatedwith said igniter and a normally open switch adapted to close when theigniter pressure difierential is such as to indicate the presence ofsuficient ignition'energy to ignite fuel admitted to said burner; secondsensingineans comprising an optical flame scanner and a normally openswitch adapted to close when said flame scanner views flame at saidburner; third sensing means including a normally open switch adapted toclose when said valve is fully open; circuit means containing saidswitches for actuating said operator including a line for opening saidvalve upon closure of the switch associated with said first sensingmeans and a line for holding said valve open upon the simultaneousclosure of the switches associated with said second and third sensingmeans.

4. The combination of a furnace chamber; a burner adapted to fire insaid furnace chamber; a fuel line connecting said burner to a fuelsource; a valve interposed in said fuel line; operator means adapted toopen and to close said valve; an igniter for igniting said burner; firstsensing means comprising a pressure differential sensor associated withsaid igniter and a normally open switch adapted to close when theigniter pressure differential is such as to indicate the presence ofsufficient ignition energy to ignite fuel admitted to said burner;second sensing means comprising an optical flame scanner and a normallyopen switch adapted to close when said flame scanner views flame at saidburner; third sensing means including a normally open switch adapted toclose when said valve is fully open; circuit means to actuate saidoperator for opening said valve including a line containing the switchassociated with said first sensing means in parallel connection with theswitches associated with said second and third sensing means.

5. in a burner system for a vapor generator having a furnace chamber, aplurality of fuel burners operative to fire in said furnace chamber,fuel lines connecting said burners to a fuel source; Valves associatedwith each of said burners in said fuel lines; an operator associatedwith each of said valves adapted to open and to close said valves; anigniter associated with each of said burners for 12 providing ignitionenergy to the fuel supplied thereto, a control system for operating eachof said valves comprising first sensing means associated with each ofsaid igniters including a first normally open switch that closes whensaid igniter exhibits sufiicient ignition energy to ignite theassociated burner and a second normally open switch that closes whensaid igniter exhibits .insufiicient ignition energy, second sensingmeans associated with each of said burners including a first normallyopen switch that closes when said burner is lighted and a secondnormally open switch that closes when said burner is not lighted, thirdsensing means associated with each of said valves including a firstlimit switch that closes when the associated valve is fully open anda'second limit switch that closes when the associated valve is not fullyopen, a first circuit for actuating the associated operator to open itsvalve containing said first switch of said first sensing means, a secondcircuit for actuating the associated operator to open its valveindependent of said first circuit containing said first switches of saidsecond and third sensing means'connected in series, a third circuit foractuating the associated operator to close its valve containing saidsecond switches of said first and second sensing means in series and afourth circuit for actuating the associated operator to close its valvecontaining said second switches of saidfirst and third sensing means inseries. 1 g

6. In a burner system for a vapor generator having a furnace chamber, aplurality of fuel burners operative to fire in said furnace chamber;fuel lines connecting said burners to a fuel source; valves associatedwith each of said burners in said fuel lines; an operator associatedwith each of said valves adapted to open and to close said valves;an'igniter associated with each of said burners for providing ignitionenergy to the fuel supplied thereto; a control system for independentlyoperating each of said valves comprising first sensing means associatedwith each of said igniters including a pressure differential sensor, afirst normally open switch that closes when said igniter exhibitssufficient differential pressure to indicate sufiicient ignition energyto ignite the associated burner and a second normally open switch thatcloses when said igniter exhibits insufiicient differential pressure;second sensing means associated with each of said burners including anoptical flame scanner, a first normally open switch that closes when theassociated flame scanner views a flame and a second normally open switchthat closes when said flame scanner views no flame; third sensing meansassociated with each of said valves including a first normally openlimit switch that closes when the associated valve is fully open and asecond normally open limit switch that closes when the associated valveis not fully open; a control circuit associated with each of saidoperators including a first line for actuating the associated operatorto open its valve containing said first switch of said first sensingmeans, a second line for actuating said operator to hold its valve opencontaining said first switches of said second and third sensing meansconnected in series, a third line for actuating said operator to closesaid valve containing said second switch of said first sensing meansconnected in series with the parallelly connected second switches ofsaid second and third sensing means.

7. A vapor generator having burners operative to fire into said furnace,a fuel source for supplying fuel to said burners, fuel lines connectingsaid burners with said fuel source, valve means in said fuel linesbetween'said burners and said fuel source, electrically actuableoperator means associated with said valve means, igniter meansassociated with each of said burners providing ignltion energy therefor,a control system comprising first sensing means associated with eachigniter toind-icate the presence of a sufiicient amount of ignitionenergy to ignite said burners, switch means associated with each of saidfirst sensing meansdactuable afurn-ace, a plurality of V i?) when thereis insufiicient ignition energy to ignite said burners, second sensingmeans associated with each burner to indicate the absence of flamethereat, switch means actuable by each of said second sensing means whenthere is no flame at the corresponding burner, electric circuit meansincluding a first line containing parallelly connected limit switchesassociated with said valve means actuable to a closed position when saidvalve means are open, a second line in parallel with said first linecontaining contacts of said first sensing means actuable switchesarranged to define a closed circuit when a predetermined number of saidfirst sensing means actuable switches are actuated, a first relayconnected in said second line and actuated upon establishment of aclosed circuit through said first sensing means actuable switches, acontact adapted to be closed by said first relay connected in serieswith said limit switches, a third line in parallel with said first andsecond lines containing contacts of said second sensing means actuableswitches arranged to define a closed circuit when a predetermined numberof said second sensing means indicate the absence of flame, a secondrelay connected in said third line and actuated upon establishment of aclosed circuit through said second sensing means actuable switches, acontact connected in series with said limit switches and said firstrelay contact adapted to be closed by said second relay, and a thirdrelay connected in series with the contacts associated with said firstand second relays adapted to close a contact to actuate said operatormeans thereby closing said valve means.

8. A vapor generator having a furnace, a plurality of burners operativeto fire into said furnace, fuel lines connecting said burners to a fuelsource, a main valve upstream of said fuel lines, valves associated witheach of said burners in said fuel lines, an electrically actuableoperator associated with said main valve, igniter means associated witheach of said burners providing ignition energy therefor, a controlsystem comprising first sensing means including a pressure differentialsensor associated with each igniter and switch means actuated by saidpressure difierential sensors when there is insufiicient ignition energyto ignite the associated burner, second sensing means including anoptical flame scanner associated with each of said burners and switchmeans actuated by said flame scanners when there is no flame at thecorresponding burner, electrical circuit means including a first linecontaining parallelly connected contacts associated with limit switcheson said valves actuable to close when the corresponding valve is open, asecond line connected in parallel with said first line containingcontacts of said pressure differential actuable switches arranged todefine a closed circuit when a predetermined number of said pressuredifferential .actuable switches are actuated, a first relay connected insaid second line and actuated upon establishment of a closed circuitthrough said pressure differential act-uable switches, a contact adaptedto be closed by said first relay connected in series with said limitswitch contacts, a third line in parallel with said first and secondlines containing contacts of said flame scanner actuable switchesarranged to define a closed circuit when a predetermined number of saidflame scanners indicate the absence of flame, a second relay connectedin said third line and actuated upon establishment of a closed circuitthrough said flame scanner actuable switches, a contact connected inseries with said limit switches and said first relay contact adapted tobe closed by said second relay and a third relay connected in serieswith the contacts associated with said first and second relays adaptedto close a contact thereby closing said main valve.

9. In a burner system for a vapor generator having a furnace chamber, aplurality of fuel burners operative to fire in said furnace chamber, amain fuel line, fuel lines connecting said burners to said main fuelline, a main valve in said main fuel line, secondary valves in saidsecareasro ondary fuel lines associated with each of said burners; anelectrically actuable operator associated with said main valve;electrically actuable operators associated with each of said burnervalves adapted to open and to close said burner valves, ignitersassociated with each of said burners providing ignition energy therefor,a control system for automatically operating said burners comprisingfirst sensing means associated with each of said igniters includingfirst normally open switch means adapted to close when the associatedigniter exhibits suifioient ignition energy to ignite its correspondingburner and second normally open switch means adapted to close when theassociated igniter exhibits insufficient ignition energy; sec,

ond sensing means associated with each of said burners including a firstnormally open switch means adapted to close when the associated burnerexhibits a flame and second normally open switch means adapted to closewhen said burner exhibits no flame; third sensing means associated witheach of said burner valves including normally open switch means adaptedto close when the corresponding valve is fully open; fourth sensingmeans operable to measure fuel pressure in said main fuel line includinga first normally open switch means adapted to close when the fuelpressure is such as to indicate the presence of a flame envelope in saidfurnace chamber and a second normally open switch means adapted to closewhen the fuel pressure is below that required for a flame envelope insaid furnace; first circuit means adapted to independently actuate eachof said burner valve operators to open the corresponding burner valveincluding, first lines connecting each of said operators to a source ofpower containing said first switch of said first sensing means of thecorresponding burner; second lines connecting each of said operators toa source of power including said first switches of said second sensingmeans and said third sensing means switches; second circuit meansadapted to be operable upon closure of the switch means associated withsaid fourth sensing means, said second circuit means including a firstline containing parallelly connected c0ntacts associated with saidswitch means of said third sensing means, a second line connected inparallel with said first line containing contacts associated with saidsecond switch means of said first sensing means arranged to define aclosed circuit when a predetermined number of said switch means areactuated, a first relay connected in said second line and actuated uponestablishment of a closed circuit through said second switch means ofsaid first sensing means, a contact adapted to be closed by said firstrelay connected in series with said switch means of said third sensingmeans, a third line in parallel with said first and second linescontaining contacts of said second switch means of said second sensingmeans arranged to define a closed circuit when a predetermined number ofsaid switch means are actuated, a second relay connected in said thirdline and actuated upon establishment of a ciosed circuit through saidsecond switch means of said second sensing means, a contact connected inseries with said switch means of said third sensing means and said firstrelay contact adapted to be closed by said second relay and a thirdrelay connected in series with the contacts associated with said firstand second relays adapted to close a contact to actuate the operator ofsaid main valve to close said main valve.

10. In a burner system for a vapor generator having a furnace chamber, aplurality of fuel burners operative to fire in said furnace chamber, amain fuel line, secondary fuel lines connecting said burner to said mainfuel line, a main valve in said main fuel line, burner valves associatedwith each of said burners in said secondary fuel lines, electricallyactuable operators associated with said main valve and said burnervalves adapted to open and to close said valves, igniters associatedwith each of said burners providing ignition energy therefor, theimprovement comprising a control system for automatically operating saidburners, said system including igniter sensors assoof said flamescanners when there is a fiame at the corresponding burner and secondswitch means actu able by each of said flame scanners when there is noflame at the corresponding burner; limit switches associated with eachof said burner valves being actuable when the corresponding burner valveis open; .a fuel pressure sensor in said main fuel line having firstswitch means actuable when the fuel pressure in said line iscapa'ble ofsupporting a flame envelope in said furnace chamber and a second switchmeans actuable when the fuel pressure is incapable of supporting a flameenvelope; first circuit means operable upon actuation of the secondswitch means of said fuel pressure sensor adapted to independentlyactuate each of, said burner valve operators to open the correspondingvalve including a first line connecting each of said operators to apower source containing contacts of said first switch means of thecorresponding igniter sensor and a second line connecting each of saidoperators to said power source including contacts of said first switchmeans of saidtigniter sensors and said flame scanners connected inseries; second circuit means operable upon actuation of the first switchmeans of said fuel pressure sensor adapted to actuate said main valveoperator including a first line containing parallelly connected contactsof said limit switches, a second line connected in parallel with saidfirst line containing contacts associated with said second switch meansof said igniter sensors arranged to define a closed circuit when apredetermined number of said switch means are actuated, .a first relayconnected 7 in said second line and actuated upon establishment of aclosed circuit through said igniter sensors second switch means, acontact adapted to be closed by said first relay connected in serieswith said limit switch contacts, a third line in parallel with saidfirst and second lines containing contacts of said second switch meansof said flame scanners arranged to define a closed circuit when apredetermined number of said switch means are actuated, a second relayconnected in said third line and actuated upon' establishment of aclosed circuit through said flame scanners second switch means, acontact connected in series with said limit switch contacts and saidfirst relay cont-act adapted to be closed by said second relay; and athird relay connected in series with said first and second relaycontacts adapted to close a contact to actuate said main valve operatorto close said main valve.

References Cited by the Examiner UNITED STATES PATENTS 2,622,669 12/52Caracristi 158-28 2,635,813 4/53 Schlenz 158-11 2,692,962 10/54 'Thomson7 158528 2,812,140 11/57 Gray 158 28 2,968,209 5/61 Mittendorf 158-283,051,227 r a 8/62 Robson 158 42.1 3,055,416 9/62 Marshall Q 15-8-28*JAMES W. WESTHAVER, Primary Examiner.

1. THE COMBINATION OF A FURNACE CHAMBER; A BURNER ADAPTED TO FIRE INSAID FURNACE CHAMBER; A FUEL LINE CONNECTING SAID BURNER TO A FUELSOURCE; A VALVE INTERPOSED IN SAID FUEL LINE; A SIGNAL RESPONSIVE VALVEOPERATOR ADAPTED TO OPEN AND TO CLOSE SAID VALVE; AN IGNITER FORIGNITING SAID BURNER; FIRST SENSING MEANS ADAPTED TO EMIT A SIGNAL WHENTHE IGNITION ENERGY OUTPUT OF SAID IGNITER IS SUFFICIENT TO IGNITE THEFUEL ADMITTED TO SAID BURNER; SECOND SENSING MEANS ASSOCIATED WITH SAIDBURNER ADAPTED TO EMIT A SIGNAL WHEN SAID BURNER EXHIBITS A FLAME; THIRDSENSING MEANS ASSOCIATED WITH SAID VALVE ADAPTED TO EMIT A SIGNAL WHENSAID VALVE IS SUBSTANTIALLY FULLY OPEN; MEANS CONNECTING SAID SENSINGMEANS AND SAID OPERATOR FOR OPENING SAID VALVE UPON RECEIPT BY SAIDOPERATOR OF A SIGNAL FROM SAID FIRST SENSING MEANS AND MEANS FOR HOLDING SAID VALVE OPEN UPON RECEIPT OF A SIGNAL FROM SAID SECOND AND THIRDSENSING MEANS.